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<div class="textblock"><code>#include &lt;<a class="el" href="types_8h_source.html">types.h</a>&gt;</code><br />
<code>#include &lt;<a class="el" href="stdint_8h_source.html">stdint.h</a>&gt;</code><br />
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<p><a href="rand_8h_source.html">Go to the source code of this file.</a></p>
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Macros</h2></td></tr>
<tr class="memitem:a690f251553b39fd4f31894826141b61a"><td class="memItemLeft" align="right" valign="top">#define&#160;</td><td class="memItemRight" valign="bottom"><a class="el" href="rand_8h.html#a690f251553b39fd4f31894826141b61a">RAND_MAX</a>&#160;&#160;&#160;255</td></tr>
<tr class="separator:a690f251553b39fd4f31894826141b61a"><td class="memSeparator" colspan="2">&#160;</td></tr>
<tr class="memitem:a6dbd2f1a15221db40f456cf574a793b4"><td class="memItemLeft" align="right" valign="top">#define&#160;</td><td class="memItemRight" valign="bottom"><a class="el" href="rand_8h.html#a6dbd2f1a15221db40f456cf574a793b4">RANDW_MAX</a>&#160;&#160;&#160;65535</td></tr>
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Functions</h2></td></tr>
<tr class="memitem:a964538799843c0ba5bd01151ef7e2640"><td class="memItemLeft" align="right" valign="top">void&#160;</td><td class="memItemRight" valign="bottom"><a class="el" href="rand_8h.html#a964538799843c0ba5bd01151ef7e2640">initrand</a> (<a class="el" href="stdint_8h.html#adf4d876453337156dde61095e1f20223">uint16_t</a> seed) <a class="el" href="asm_2types_8h.html#a0971918860055db2e50dacea4da8f3bc">OLDCALL</a></td></tr>
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<tr class="memitem:aec33f1e833f8bee2678dc33873af870d"><td class="memItemLeft" align="right" valign="top"><a class="el" href="stdint_8h.html#aba7bc1797add20fe3efdf37ced1182c5">uint8_t</a>&#160;</td><td class="memItemRight" valign="bottom"><a class="el" href="rand_8h.html#aec33f1e833f8bee2678dc33873af870d">rand</a> (void) <a class="el" href="asm_2types_8h.html#a0971918860055db2e50dacea4da8f3bc">OLDCALL</a> <a class="el" href="asm_2types_8h.html#acb825e83a33fcc06482c59b4ab2cf961">PRESERVES_REGS</a>(<a class="el" href="sms_8h.html#a4c2e4adef74067fdbb49005bc73de937">b</a></td></tr>
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<tr class="memitem:a2407b9d841bd78b0064eceafdc188467"><td class="memItemLeft" align="right" valign="top"><a class="el" href="stdint_8h.html#adf4d876453337156dde61095e1f20223">uint16_t</a>&#160;</td><td class="memItemRight" valign="bottom"><a class="el" href="rand_8h.html#a2407b9d841bd78b0064eceafdc188467">randw</a> (void) <a class="el" href="asm_2types_8h.html#a0971918860055db2e50dacea4da8f3bc">OLDCALL</a> <a class="el" href="asm_2types_8h.html#acb825e83a33fcc06482c59b4ab2cf961">PRESERVES_REGS</a>(<a class="el" href="sms_8h.html#a4c2e4adef74067fdbb49005bc73de937">b</a></td></tr>
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<tr class="memitem:a333400f85febd7e1360835955103db8b"><td class="memItemLeft" align="right" valign="top">void&#160;</td><td class="memItemRight" valign="bottom"><a class="el" href="rand_8h.html#a333400f85febd7e1360835955103db8b">initarand</a> (<a class="el" href="stdint_8h.html#adf4d876453337156dde61095e1f20223">uint16_t</a> seed) <a class="el" href="asm_2types_8h.html#a0971918860055db2e50dacea4da8f3bc">OLDCALL</a></td></tr>
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<tr class="memitem:a4a5e355fc122d90d6225503b5ed796ad"><td class="memItemLeft" align="right" valign="top"><a class="el" href="stdint_8h.html#aba7bc1797add20fe3efdf37ced1182c5">uint8_t</a>&#160;</td><td class="memItemRight" valign="bottom"><a class="el" href="rand_8h.html#a4a5e355fc122d90d6225503b5ed796ad">arand</a> (void) <a class="el" href="asm_2types_8h.html#a0971918860055db2e50dacea4da8f3bc">OLDCALL</a> <a class="el" href="asm_2types_8h.html#acb825e83a33fcc06482c59b4ab2cf961">PRESERVES_REGS</a>(<a class="el" href="sms_8h.html#a4c2e4adef74067fdbb49005bc73de937">b</a></td></tr>
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Variables</h2></td></tr>
<tr class="memitem:a7aab2f4a234108a5eae48e0d26380ae7"><td class="memItemLeft" align="right" valign="top"><a class="el" href="stdint_8h.html#adf4d876453337156dde61095e1f20223">uint16_t</a>&#160;</td><td class="memItemRight" valign="bottom"><a class="el" href="rand_8h.html#a7aab2f4a234108a5eae48e0d26380ae7">__rand_seed</a></td></tr>
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<a name="details" id="details"></a><h2 class="groupheader">Detailed Description</h2>
<div class="textblock"><p>Random generator using the linear congruential method</p>
<dl class="section author"><dt>Author</dt><dd>Luc Van den Borre </dd></dl>
</div><h2 class="groupheader">Macro Definition Documentation</h2>
<a id="a690f251553b39fd4f31894826141b61a"></a>
<h2 class="memtitle"><span class="permalink"><a href="#a690f251553b39fd4f31894826141b61a">&#9670;&nbsp;</a></span>RAND_MAX</h2>

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          <td class="memname">#define RAND_MAX&#160;&#160;&#160;255</td>
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<h2 class="memtitle"><span class="permalink"><a href="#a6dbd2f1a15221db40f456cf574a793b4">&#9670;&nbsp;</a></span>RANDW_MAX</h2>

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          <td class="memname">#define RANDW_MAX&#160;&#160;&#160;65535</td>
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<h2 class="groupheader">Function Documentation</h2>
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<h2 class="memtitle"><span class="permalink"><a href="#a964538799843c0ba5bd01151ef7e2640">&#9670;&nbsp;</a></span>initrand()</h2>

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          <td class="memname">void initrand </td>
          <td>(</td>
          <td class="paramtype"><a class="el" href="stdint_8h.html#adf4d876453337156dde61095e1f20223">uint16_t</a>&#160;</td>
          <td class="paramname"><em>seed</em></td><td>)</td>
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<p>Initalise the pseudo-random number generator.</p>
<dl class="params"><dt>Parameters</dt><dd>
  <table class="params">
    <tr><td class="paramname">seed</td><td>The value for initializing the random number generator.</td></tr>
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  </dd>
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<p>The seed should be different each time, otherwise the same pseudo-random sequence will be generated.</p>
<p>One way to do this is sampling (<a class="el" href="gb_2hardware_8h.html#afa1e18e47bf68ce68d7807fff6edf16b">DIV_REG</a>) up to 2 times (high byte of seed value then the low byte) at variable, non-deterministic points in time (such as when the player presses buttons on the title screen or in a menu).</p>
<p>It only needs to be called once to be initialized.</p>
<dl class="section see"><dt>See also</dt><dd><a class="el" href="rand_8h.html#aec33f1e833f8bee2678dc33873af870d">rand()</a>, <a class="el" href="rand_8h.html#a2407b9d841bd78b0064eceafdc188467">randw()</a> </dd></dl>

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<h2 class="memtitle"><span class="permalink"><a href="#aec33f1e833f8bee2678dc33873af870d">&#9670;&nbsp;</a></span>rand()</h2>

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          <td class="memname"><a class="el" href="stdint_8h.html#aba7bc1797add20fe3efdf37ced1182c5">uint8_t</a> rand </td>
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<p>Returns a random byte (8 bit) value.</p>
<p><a class="el" href="rand_8h.html#a964538799843c0ba5bd01151ef7e2640">initrand()</a> should be used to initialize the random number generator before using <a class="el" href="rand_8h.html#aec33f1e833f8bee2678dc33873af870d">rand()</a> </p>

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<h2 class="memtitle"><span class="permalink"><a href="#a2407b9d841bd78b0064eceafdc188467">&#9670;&nbsp;</a></span>randw()</h2>

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          <td class="memname"><a class="el" href="stdint_8h.html#adf4d876453337156dde61095e1f20223">uint16_t</a> randw </td>
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<p>Returns a random word (16 bit) value.</p>
<p><a class="el" href="rand_8h.html#a964538799843c0ba5bd01151ef7e2640">initrand()</a> should be used to initialize the random number generator before using <a class="el" href="rand_8h.html#aec33f1e833f8bee2678dc33873af870d">rand()</a> </p>

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<h2 class="memtitle"><span class="permalink"><a href="#a333400f85febd7e1360835955103db8b">&#9670;&nbsp;</a></span>initarand()</h2>

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          <td class="memname">void initarand </td>
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          <td class="paramtype"><a class="el" href="stdint_8h.html#adf4d876453337156dde61095e1f20223">uint16_t</a>&#160;</td>
          <td class="paramname"><em>seed</em></td><td>)</td>
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<p>Random generator using the linear lagged additive method</p>
<dl class="params"><dt>Parameters</dt><dd>
  <table class="params">
    <tr><td class="paramname">seed</td><td>The value for initializing the random number generator.</td></tr>
  </table>
  </dd>
</dl>
<p>Note: <a class="el" href="rand_8h.html#a333400f85febd7e1360835955103db8b">initarand()</a> calls <a class="el" href="rand_8h.html#a964538799843c0ba5bd01151ef7e2640">initrand()</a> with the same seed value, and uses <a class="el" href="rand_8h.html#aec33f1e833f8bee2678dc33873af870d">rand()</a> to initialize the random generator.</p>
<dl class="section see"><dt>See also</dt><dd><a class="el" href="rand_8h.html#a964538799843c0ba5bd01151ef7e2640">initrand()</a> for suggestions about seed values, <a class="el" href="rand_8h.html#a4a5e355fc122d90d6225503b5ed796ad">arand()</a> </dd></dl>

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<h2 class="memtitle"><span class="permalink"><a href="#a4a5e355fc122d90d6225503b5ed796ad">&#9670;&nbsp;</a></span>arand()</h2>

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<p>Returns a random number generated with the linear lagged additive method.</p>
<p><a class="el" href="rand_8h.html#a333400f85febd7e1360835955103db8b">initarand()</a> should be used to initialize the random number generator before using <a class="el" href="rand_8h.html#a4a5e355fc122d90d6225503b5ed796ad">arand()</a> </p>

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<h2 class="groupheader">Variable Documentation</h2>
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<h2 class="memtitle"><span class="permalink"><a href="#a7aab2f4a234108a5eae48e0d26380ae7">&#9670;&nbsp;</a></span>__rand_seed</h2>

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          <td class="memname"><a class="el" href="stdint_8h.html#adf4d876453337156dde61095e1f20223">uint16_t</a> __rand_seed</td>
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<p>The random number seed is stored in __rand_seed and can be saved and restored if needed.</p>
<div class="fragment"><div class="line"><span class="comment">// Save</span></div>
<div class="line">some_uint16 = <a class="code" href="rand_8h.html#a7aab2f4a234108a5eae48e0d26380ae7">__rand_seed</a>;</div>
<div class="line">...</div>
<div class="line"><span class="comment">// Restore</span></div>
<div class="line">__rand_seed = some_uint16;</div>
<div class="ttc" id="arand_8h_html_a7aab2f4a234108a5eae48e0d26380ae7"><div class="ttname"><a href="rand_8h.html#a7aab2f4a234108a5eae48e0d26380ae7">__rand_seed</a></div><div class="ttdeci">uint16_t __rand_seed</div></div>
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